Marine propeller applicable to all speed ranges

ABSTRACT

An all speed range propeller includes a propeller hub and plural propeller blades having their shafts symmetrically connected with the propeller hub. Each propeller blade is divided into a first region and a second region from the propeller hub to an outer end. The first region and the second region are different in wing structure, and the wing cross-sectional area of the second region is smaller than that of the first region. Thus, in speed ranges that common ships navigate most frequently, the all speed range propeller of this invention can lower the influence of cavitation produced because of different speed ranges, able to maintain high efficiency in use and prevent the efficiency of the propeller from lowered exceedingly.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a marine propeller.

2. Description of the Prior Art

Conventionally, marine propellers are mainly categorized as NACA seriespropellers, KCA series propellers and Super-cavitating seriespropellers. Referring to FIG. 1, through viscous flow analysis andcavitation module analysis, it is found that when the surface ratio ofthe NACA series propeller is 1.0 and the speed range is 20 knots, theefficiency of the propeller is 0.72, and when the speed range is up to40 knots, the efficiency is only 0.5. Obviously, when the NACA seriespropeller is operated in different speed ranges, the efficiency of thepropeller will drop sharply because of cavitation, and it can also befound that the conventional propellers like the NACA series propellercan produce best efficacy only at some speed ranges, and once it goesbeyond these ranges, its efficacy will drop greatly. In addition, thepropellers employed by common ships are mostly NACA series propellers orKCA series propellers when the speed is under 30 knots, while thesuper-cavittating series propellers are mainly adopted if the speed isover 30 knots. However, for the present, the most frequent navigationspeed of common ships is between 20 and 40 knots; therefore, if the NACAseries propeller or the KCA series propeller is adopted and thenavigation speed is over 30 knots, not only the efficacy of thepropellers will be lowered greatly because of cavitation, but also thesurfaces of propeller will produce numerous burst bubbles due tocavitation and make the ship body vibrate.

SUMMARY OF THE INVENTION

The objective of this invention is to offer an all speed range propellerapplicable to high and low speed ranges. The all speed range propelleris composed of a propeller hub and a plurality of propeller bladeshaving their shafts symmetrically connected with the propeller hub. Eachpropeller blade is formed with an upper surface and a lower surface,which have a junction of their front half section formed into a wingfront edge and a junction of their rear half section formed into a wingrear edge. Each propeller blade is divided into a first region and asecond region extending from the propeller hub to an outer end, and thefirst region and the second region are different in wing structure andthe wing cross-sectional area of the second region is smaller than thatof the first region. The propeller blades are radially combined with thepropeller hub.

Each propeller blade contains two kinds of wing structures to make up anall speed range propeller. In speed ranges that ships navigate mostfrequently, the all speed range propeller of this invention can lowerthe influence of cavitation produced because of different speed ranges,able to maintain high efficiency in use and prevent the efficiency ofthe propeller from being lowered excessively.

BRIEF DESCRIPTION OF DRAWINGS

This invention will be better understood by referring to theaccompanying drawings, wherein:

FIG. 1 is a perspective view of a conventional NACA propeller;

FIG. 2 is a front view of a first preferred embodiment of an all speedrange propeller in the present invention;

FIG. 3 is a cross-sectional view of the line B-B in FIG. 2;

FIG. 4 is a cross-sectional view of the line A-A in FIG. 2;

FIG. 5 is a cross-sectional view of a second preferred embodiment of theline A-A in FIG. 2;

FIG. 6 is a distribution curve of the torsion (KQ) of an all speed rangepropeller in the present invention;

FIG. 7 is a distribution curve of the thrust of the all speed rangepropeller in the present invention; and

FIG. 8 is a distribution curve of the pressure of the all speed rangepropeller in the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A first preferred embodiment of an all speed range propeller 100 in thepresent invention, as shown in FIGS. 2-4, is composed of a propeller hub200 and a plurality of propeller blades 10 having their shaftssymmetrically connected with the propeller hub 200. In this preferredembodiment, the all aped range propeller 100 is provided with fourpropeller blades 10 respectively formed with an supper surface 11 and alower surface 12, and the junction of the front half section of theupper surface 11 and the lower surface 12 is formed into a wing frontedge 13, and a junction of the rear half section of them is formed intoa wing rear edge 14. Each propeller blade 10 is divided into a firstregion 15 and a second region 16 extending from the propeller hub 200 toan outer end. The first region 15 and the second region 16 of eachpropeller blade 10 are different in wing structure, and the wing crosssectional area of the second region 16 is smaller than that of the firstregion 15. Then, such designed propeller blades 10 are radially combinedwith the propeller hub 200 to form an all speed range propeller 100.

Referring to FIG. 3, in this preferred embodiment, the first region 15has its upper surface formed with an upper convex-curved portion 151extending from the wing front edge 13 to the wing rear edge 14, and therear half section of its lower surface formed with a first lower convexportion 152 extending toward the wing rear edge 14. Further, the uppersurface and the lower surface of the second region 16 are formed with atleast one concave portion. Referring to FIG. 4, in this preferredembodiment, a front half section of the upper surface of the secondregion 16 is formed with an upper even-smooth portion 161 and a rearhalf section is formed with a first upper concave portion 162 stretchingtoward the wing rear edge 14. Furthermore, a front half section of thelower surface of the second region 16 is formed into a lower even-smoothportion 163 and a rear half section formed into a second lower convexportion 164 stretching toward the wing rear edge 14.

A second preferred embodiment of an all speed range propeller 100 in thepresent invention, as shown in FIG. 5, is to have a rear half section ofthe upper surface of the second region 16 formed with a second upperconcave portion 165 extending toward the wing rear edge 14, and a fronthalf section of the lower surface of the second region 16 formed with alower concave portion 166 extending toward the wing rear edge 14, makingthe second region 16 into an S-shaped wing structure.

In addition, each propeller blade 10 has an intermediate portion formedwith a central region 17 that has its upper surface and lower surfaceconnected between the first region 15 and the second region 16 withgreat-extent curvature changes so that the mutually jointing surface ofthe first region 15 with the second region 16 can be formed into acircular and smooth curve and avoid forming an irregular surfacetherebetween, letting the all speed range propeller 100 look beautifulin a appearance. Moreover, the central region 17 is a very small regionconnected between the first region 15 and the second region 16, able toreduce influence to the propeller 100 while it is operated and thusenabling the all speed range propeller 100 to attain optimized efficacyof operation.

Referring to FIGS. 3-5, the second region 16 of each propeller blade 10is lighter and thinner than the first region 15, thus effectivelylessening the whole weight of each propeller blade 10 and lowering theturning moment from each propeller blade 10 to the propeller hub 200.Therefore, when the propeller hub 200 is started to rotate, eachpropeller 10 can be rotated faster than a conventional propeller.

In addition, referring to FIGS. 3 and 4, the upper surface of the firstregion 15 has a location adjacent to the wing rear edge 14 defined to bean upper apex 153, and the lower surface of the first region 15 has alocation adjacent to the wing rear edge 14 defined to be a lower apex154. When the all speed range propeller 100 is rotated at intermediateand high speed ranges, cavitation bubbles will be formed at bothlocations of the upper apex 153 and the lower apex 154 of the firstregion 15 of the all speed range propeller unit 100, and foresaidcavitation bubbles will form a cavitation bubble area stretching towardthe wing rear edge 14. Meanwhile, cavitation bubbles will also be formedat the first upper concave-curved portion 162 of the upper surface andat the second lower convex-curved portion 164 of the lower surface ofthe second region 16, and foresaid cavitation bubbles will form acavitation bubble area.

On the other hand, when the all speed range propeller 100 is rotated atlow and intermediate speed ranges, the lift coefficient of a unit areaof each propeller blade 10 becomes large, able to decrease the area ofeach propeller blade 10 and equally attaining the same efficiency as theNACA series propeller and thus saving cost of materials.

Moreover, referring to FIGS. 6, 7 and 8 that are distribution diagramsof the torsion (KQ), the thrust (KT) and the pressure (−CP) of the allspeed range propeller. It can be seen from FIGS. 6 and 7 that the curvesof the torsion and the thrust of the all speed range propeller of thisinvention, after cavitating and at speeds of 30 and 40 knots, are higherthan the curve of the torsion and the thrust of the propeller beforecavitating and at a speed of 20 knots. Apparently, the all speed rangepropeller 100 of this invention has excellent thrust and torsion eitherbefore or after cavitation, applicable to all speed ranges.Additionally, FIG. 8 is a diagram of a pressure distribution area of thepropeller at a section where the radius is 0.7 R. It is found that thepressure distribution area, before cavitating and at a speed of 20knots, will produce state of pressure reverse turn at the end of thepropeller to offset the whole pressure area, but after cavitating and ata speed of 30 knots, the pressure at the end of the propeller will notturned reversely and the pressure distribution area is larger than thatbefore cavitating and at a speed of 20 knots. Contrasting the pressuredistribution area of the propeller in FIG. 8 with the thrustdistribution of the propeller in FIG. 7, it can be found that the sizeof the pressure area can be homologized with the surface of the thrust.

While the preferred embodiments of the invention have been describedabove, it will be recognized and understood that various modificationsmay be made therein and the appended claims are intended to cover allsuch modifications that may fall within the spirit and scope of theinvention.

What is claimed is:
 1. An all speed range propeller comprising apropeller hub and a plurality of propeller blades, said propeller bladeshaving their shafts symmetrically connected with said propeller hub,each said propeller blade having an upper surface and a lower surface,said upper surface and said lower surface having a junction of theirfront half section formed into a wing front edge, said upper surface andsaid lower surface having a junction of their rear half section formedinto a wing rear edge; and characterized by, each said propeller bladedivided into a first region and a second region in a direction from saidpropeller hub to an outer end, said first region and said second regiondifferent in wing structure and said each said propeller blade radiallycombined on said propeller hub, wing cross-sectional area of said secondregion smaller than that of said first region, in speed ranges thatcommon ships navigate most frequently said all speed range propellerable to lower influence of cavitation produced due to different speedranges, said all speed range propeller able to maintain high efficiencyin use when operated in different speed ranges.
 2. The all speed rangepropeller as claimed in claim 1, wherein said upper surface of saidfirst region is formed with an upper convex portion extending from saidwing front edge to said wing rear edge while a rear half section of saidlower surface of said first region is formed with a lower convex portionstretching toward said wing rear edge, and said upper surface and saidlower surface of said second region are formed with at least one concaveportion.
 3. The all speed range propeller as claimed in claim 1, whereina front half section of said upper surface of said second region isformed with an upper even-smooth portion and a rear half section isformed with an upper concave portion extending toward said wing rearedge, a front half section of said lower surface of said second regionformed with a lower even-smooth portion, a rear half section of saidlower surface of said second region formed with a lower convex portionextending toward said wing rear edge.
 4. The all speed range propelleras claimed in claim 2, wherein a rear half section of said upper surfaceof said second region is formed with an upper concave portion stretchingtoward said wing rear edge and a front half section of said lowersurface of said second region is formed with a lower concave portionextending toward said wing rear edge, letting said second regiongenerally formed into a S-shaped wing structure.
 5. The all speed rangepropeller as claimed in claim 1, wherein each said propeller blade isfurther formed with a central region having an upper surface and a lowersurface connected between said first region and said second region withgreat curvature change.
 6. An all speed range propeller comprising apropeller hub and plural propeller blades having their shaftssymmetrically connected with said propeller hub, each said propellerblade having an upper surface and a lower surface, said upper surfaceand said lower surface having a junction location of their front halfsection formed into a wing front edge, said upper surface and said lowersurface having a junction location of their rear half section formedinto a wing rear edge; and characterized by, each said propeller bladedivided into a first region and a second region from said propeller hubto an outer end, said first region and said second region different inwing structure, said propeller blades radially combined with saidpropeller hub, wing cross-sectional area of said second region beingsmaller than that of said first region, said upper surface of said firstregion of said all speed range propeller having a location adjacent tosaid wing rear edge defined to be an upper apex, said lower surface ofsaid first region having a location adjacent to said wing rear edgedefined to be a lower apex, cavitation bubbles formed at said upper apexand said lower apex of said first region when said all speed rangepropeller is rotated at intermediate and high speed ranges, saidcavitation bubbles formed into a cavitation bubble area stretchingtoward said wing rear edge, said upper surface of said second regionhaving a location adjacent to said wing rear edge defined to be a lowerconvex surface where cavitation bubbles are formed, said cavitationbubbles formed into a cavitation bubble area stretching toward said wingrear edge.
 7. An all speed range propeller comprising a propeller huband plural propeller blades that have their shafts symmetricallyconnected with said propeller hub, each said propeller blade having anupper surface and a lower surface, said upper surface and said lowersurface having a junction of their front half section formed into a wingfront edge, said upper surface and said lower surface having a junctionlocation of their rear half section formed into a wing rear edge; andcharacterized by, each said propeller blade divided into a first regionand a second region from said propeller hub to an outer end, said firstregion and said second region different in wing structure, saidpropeller blades radially combined with said propeller hub, wingcross-sectional area of said second region smaller than that of saidfirst region, lift coefficient of a unit area of each said propellerblade becoming great when said all speed range propeller is rotated atlow and intermediate speed ranges, able to lessen area of each saidpropeller blade.